This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Human clinical trials of DCE-MRI at the University of Pennsylvania and at other institutions have demonstrated the usefulness of DCE-MRI as a prognostic biomarker for renal cell carcinoma tumor response to sorafenib, a receptor tyrosine kinase inhibitor with anti-angiogenic properties. The project seeks to further the mechanistic studies of DCE-MRI as a biomarker of tumor angiogenic activity and response to targeted anti-angiogenic agents in RCC. Specifically, this project will identify the concordance of DCE-MRI metrics with non-invasive in vivo PET imaging of carbonic anhydrase IX (a molecular marker of VHL-HIF pathway deregulation) and histocytometric analysis of endothelial cell activation in RCC. This project will also compare the ability of DCE-MRI and PET imaging to predict response of RCC to novel second line tyrosine kinase inhibitors currently in clinical use or under evaluation.